4.0.0 HP Polyserve Matrix Server Installation Guide (T5392-96046, March 2010)
“prefer” to have I/O operations occur on natural block boundaries, such as 4-KB
blocks. If a partition starts at a non-block boundary, a single logical write can span
more physical blocks that it would on a partition starting on a block boundary,
resulting in additional I/O operations. The exact alignment characteristics vary by
manufacturer and model; consult your storage vendor for alignment recommendations.
This issue occurs because the Windows partition table causes space to be reserved
at the start of the LUN, which can cause a misalignment with the array’s storage. If
your storage array is affected by this issue, the simplest way to avoid the situation
is to create an unused partition at the start of the LUN and then ensure that the second
partition starts on an aligned boundary. The Windows Logical Disk Manager or
utilities such as diskpart can be used to create the partitions.
Partitions containing Windows filesystems
If you will be using an existing partition for a membership partition and that partition
currently contains a Windows filesystem, then that filesystem must be destroyed. One
method for doing this is to delete the partition and then recreate it. This is best done
before multiple servers have access to the disk. If that is not possible, all other servers
with access to the disk must be forced to recognize the changes, either by rebooting
all those systems, or by manually disabling the ports on the FibreChannel switch that
connect those systems to the SAN. If using the second method, disable the ports
before making the partition table change, and then reenable the ports afterwards.
Changes to the disk partition table
We recommend that you do all necessary partitioning on disks that will contain
membership partitions before assigning the membership partitions. It is best to do
the partitioning before multiple servers have access to the disk. If this is not possible,
ensure that all servers having access to the disk through the SAN detect the partition
table changes before continuing on with membership partition initialization.
This can be done either by rebooting the servers after you make the partition table
changes, or by manually disabling the ports on the FibreChannel switch that connect
the servers to the SAN. If using the second method, disable the ports before making
the partition table changes, and then reenable the ports afterwards.
If you should later need to repartition a disk containing a membership partition, you
will need to stop Matrix Server before you change the layout. While the matrix is
stopped, you will not be able to access other disks in the matrix. When Matrix Server
is restarted on the server, it will recognize the changes to the partition table. (You
will need to restart Matrix Server on each node to enable it to see the changes.)
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